Information concerning the formation and structure of human casein micelles is approximately at the level reached ten to fifteen years ago with the bovine caseins. Using the bovine casein system as a guide, this research project will systematically investigate the human casein system. First, purification procedures will be established for the major components. The monomer caseins will then be characterized as to size and shape by analytical ultracentrifugation and viscosity and the amino acid composition will be determined. Calcium binding under various conditions will be measured with radioactive tracers and this will be correlated to the extent of monomer-monomer interaction. Micelle and possible submicelle formation will be studied in the presence of inorganic phosphate and calcium with the hope of divising a suitable molecular model to describe the process. Such a model can direct further productive experimentation and provide insight into the variety of ways proteins can interact to fulfill specific functions. Comparison of the human system and the bovine system can be made to determine how well the latter supplies the nutritional needs of the human infant.